This invention is an improvement over my prior U.S. Pat. No. 4,081,012, and over Johnson Pat. No. 2,939,805.
In my prior patent, there is disclosed a threaded fastener having fluid, unreacted epoxy resin deposited within thread grooves thereof extending only part way around the fastener, and a fluid activating or polymerizing agent deposited within the thread grooves directly adjacent the epoxy deposit. These two fluid deposits flow together, and where they abut, they react to form a solid barrier film which prevents further reaction until the two fluid materials are intermixed by threading together two mating threaded fasteners, one of which is modified as described above.
The prior patent discloses the use of a protective, non-tacky cover film overlying the deposits of fluid epoxy and activator, which is preferably polyvinyl alcohol (PVA), and is applied in an aqueous solution as a spray.
Johnson U.S. Pat. No. 2,939,805 discloses and claims a self locking bolt, two component fastening elements having ". . . mutually engageable surfaces . . . " (the threads) and ". . . two discrete mutually polymerizable coatings between said surfaces adapted to be . . . mixed together during engagement of said surfaces to form a polymerized mass effectively locking said surfaces . . . ".
The coatings may be deposited by "spraying, dipping and the like" and "are adapted to form a polymerized mixture and when mixed, preferably form a metal-to-metal adhesive."
The patent sets out two Examples. In Example 1, an epoxy resin is "heated to a liquid form and a threaded bolt shank is dipped into it to form a single coating." The second superimposed coating is applied only after the liquid epoxy coating has cooled, which is understood to mean that it is changed from its liquid condition to which it was heated to a solid. The second coating is applied by dipping into a solution of a polyamide in methyl isobutyl carbinol.
The patent states that a polymeric membrane was substantially immediately formed between the two coatings because they are "mutually reactive".
Evidently Johnson's product is completed by evaporation of the solvent, since there is no suggestion that either coating, the epoxy resin or the polyamide solution remain fluid. More significant is the fact that Johnson provides no protective cover material over the coatings.
In his second Example, Johnson teaches forming a 70% solids solution of a product formed by reacting 5 mols of totylene diisocyanate with 1 mol of trimethylol propane and 1 mol of 1, 4 hexane diol. The bolt is dipped in this solution and "allowed to dry." The second coating is applied by dipping the bolt in a specific alkyd resin. There is no suggestion that the alkyd resin remains fluid, and the absence of any protective cover indicates that neither of the coating remains fluid or are designed for immediate use.
In my prior U.S. Pat. No. 4,081,012, I have disclosed the deposit of a fluid epoxy resin and a fluid activator circumferentially in contiguous areas. Where these materials come into contact with each other, there is formed a barrier film which prevents intermixture of these deposits until the fasteners are brought together. To protect these deposits, at least one of which remains fluid, a thin protective cover film, specifically PVA, is applied.
In accordance with the present invention, a new product in the form of a threaded fastener having in an annular zone extending completely around the fastener, superimposed deposits both of which also extend completely around the fastener and which react to form an annular barrier film extending between the deposits to prevent intermixture thereof. The deposits, which remain fluid, have a non-tacky protective cover film over the deposits.
The production of these fateners is accomplished on a single, short production line, in which a succession of bolts are advanced on a conveyor through stations which apply a deposit of at least partly unreacted fluid epoxy resin, a deposit of fluid activator, a deposit of a film-forming aqueous solution of protective material such as PVA, and an application of a quick drying powder such as guar to the film forming material.